Known automatic or automated motor vehicle transmissions include a parking lock with which the driven shaft of a transmission can be mechanically locked. In addition to a purely mechanical system to actuate such a parking lock by way of a mechanical functional connection between a selector lever that can be operated by the driver in the interior of the motor vehicle and the parking lock in the transmission, electromechanical and electrohydraulic systems for actuating such a parking lock are known for example from DE 41 27 991 C2. The parking lock in the transmission is connected, via an electrical functional connection, to a selector device in the interior of the motor vehicle operated by the driver. The parking lock can be electromechanically or electrohydraulically actuated by way of a parking lock function implemented in an electronic control device of the transmission depending on a gear chosen on the selector device and depending on other operating parameters of the motor vehicle.
In addition, numerous methods are known for automatically setting such a parking lock. In U.S. Pat. No. 3,937,105, it is thus proposed to automatically set the parking position of the transmission independently from the gear selected by the driver, when the current in an ignition circuit of the motor vehicle is interrupted and the vehicle simultaneously continues to roll at a speed less than a defined low threshold value.
A method is known from U.S. Pat. No. 4,892,014 in which the parking lock of the transmission is automatically set by an electric motor, if an ignition circuit of the motor vehicle is interrupted and the vehicle speed simultaneously is less than a defined low threshold value, but also if the driver's door of the motor vehicle is open and the driver seat simultaneously has no weight on it and simultaneously the vehicle speed is less than the above-mentioned low threshold value. In both cases, it is envisioned that, upon automatically setting the parking lock, a vehicle parking brake is also automatically actuated. In U.S. Pat. No. 4,892,014, it is also proposed that, if the ignition circuit is closed without the drive motor of the motor vehicle running, the transmission is automatically shifted to the neutral position by an electric motor without the driver having to take any action.
Finally, a function for automatically setting a parking lock of an automatic transmission is known from EP 0 814 287 B1 in which the parking lock in the automatic transmission is automatically set by the transmission control device, if the vehicle speed of the motor vehicle is zero and an ignition circuit is simultaneously interrupted and, as a simultaneous additional condition, a predetermined time span since the interruption of the of the ignition circuit has expired, or a vehicle door is opened, but at the latest, however this being a sole condition if the ignition key is removed from the ignition lock. In order to obtain greater vehicle reliability, as a peculiarity in all three cases setting the parking lock is prevented if the driver selects neutral with the selector device directly before shutting off the motor or within a predetermined time span after shutting off the motor.
The present invention has the task of creating an alternative method to the state of the art for the automatic selection of the neutral position in an automatic or automated transmission of a motor vehicle and for the automatic selection of a parking device of the motor vehicle provided to immobilize the motor vehicle with sufficient safeguarding of the motor vehicle against a starting or rolling unintended by the driver and with as slight as possible impairment of the vehicle's drivability or ability to move with avoidance of any change of the operating condition of the transmission or motor vehicle that might surprise the driver.